Reusable secondary batteries have been used as power sources of portable electronic devices, mobile telecommunication devices, etc., to save resources and energy. Use of such secondary batteries as power sources of vehicles etc. has been considered to reduce an amount of fossil fuel used, an amount of CO2 emission, etc.
In particular, a technology of connecting general-purpose batteries in parallel or series to constitute battery modules, and combining the battery modules for a wide variety of uses has practically been employed. According to the technology, the battery modules can be downsized and reduced in weight by improving performance of the batteries (cells) constituting the battery modules. This can advantageously improve workability in combining the battery modules, a degree of freedom in mounting the battery modules in limited space in the vehicle, etc.
When the cells are arranged to be close to each other, the battery module can be increased in energy density, and can be downsized. However, if one of the cells experienced an internal short circuit etc., and abnormally generated heat (hereinafter merely referred to as “in the event of abnormal heat generation”), normal cells around the abnormally heated cell (abnormal cell) are exposed to high temperature, and chained abnormal heat generation may possibly occur. Patent Document 1 proposes a cooling tube capable of releasing a coolant in the event of the abnormal heat generation. The cooling tube is configured to partially melt in the event of the abnormal heat generation, and the coolant is released when the cooling tube is molten.